Add curved LineDataSet Chart

@@ -3,6 +3,7 @@
 ## 1.8.0
 
 - Improve Table.fromTextArray()
+- Add curved LineDataSet Chart
 
 ## 1.7.1
 

@@ -30,6 +30,9 @@ export 'package:barcode/barcode.dart';
 part 'widgets/annotations.dart';
 part 'widgets/barcode.dart';
 part 'widgets/basic.dart';
+part 'widgets/chart/chart.dart';
+part 'widgets/chart/linear_grid.dart';
+part 'widgets/chart/line_chart.dart';
 part 'widgets/clip.dart';
 part 'widgets/container.dart';
 part 'widgets/content.dart';
@@ -54,4 +57,3 @@ part 'widgets/text_style.dart';
 part 'widgets/theme.dart';
 part 'widgets/widget.dart';
 part 'widgets/wrap.dart';
-part 'widgets/chart.dart';

+/*
+ * Copyright (C) 2017, David PHAM-VAN <dev.nfet.net@gmail.com>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// ignore_for_file: omit_local_variable_types
+
+part of widget;
+
+class Chart extends Widget {
+  Chart({
+    @required this.grid,
+    @required this.data,
+  });
+
+  final ChartGrid grid;
+
+  final List<DataSet> data;
+
+  PdfPoint _computeSize(BoxConstraints constraints) {
+    if (constraints.isTight) {
+      return constraints.smallest;
+    }
+
+    double width = constraints.maxWidth;
+    double height = constraints.maxHeight;
+
+    const double aspectRatio = 1;
+
+    if (!width.isFinite) {
+      width = height * aspectRatio;
+    }
+
+    if (!height.isFinite) {
+      height = width * aspectRatio;
+    }
+
+    return constraints.constrain(PdfPoint(width, height));
+  }
+
+  @override
+  void layout(Context context, BoxConstraints constraints,
+      {bool parentUsesSize = false}) {
+    box = PdfRect.fromPoints(PdfPoint.zero, _computeSize(constraints));
+
+    grid.layout(context, box.size);
+  }
+
+  @override
+  void paint(Context context) {
+    super.paint(context);
+
+    final Matrix4 mat = Matrix4.identity();
+    mat.translate(box.x, box.y);
+    context.canvas
+      ..saveContext()
+      ..setTransform(mat);
+
+    grid.paintBackground(context, box.size);
+    for (DataSet dataSet in data) {
+      dataSet.paintBackground(context, grid);
+    }
+    for (DataSet dataSet in data) {
+      dataSet.paintForeground(context, grid);
+    }
+    grid.paintForeground(context, box.size);
+    context.canvas.restoreContext();
+  }
+}
+
+abstract class ChartGrid {
+  void layout(Context context, PdfPoint size);
+  void paintBackground(Context context, PdfPoint size);
+  void paintForeground(Context context, PdfPoint size);
+
+  PdfPoint tochart(PdfPoint p);
+}
+
+@immutable
+abstract class ChartValue {
+  const ChartValue();
+}
+
+abstract class DataSet {
+  void paintBackground(Context context, ChartGrid grid);
+  void paintForeground(Context context, ChartGrid grid);
+}

+/*
+ * Copyright (C) 2017, David PHAM-VAN <dev.nfet.net@gmail.com>
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// ignore_for_file: omit_local_variable_types
+
+part of widget;
+
+class LineChartValue extends ChartValue {
+  const LineChartValue(this.x, this.y);
+  final double x;
+  final double y;
+
+  PdfPoint get point => PdfPoint(x, y);
+}
+
+class LineDataSet extends DataSet {
+  LineDataSet({
+    @required this.data,
+    this.pointColor,
+    this.pointSize = 3,
+    this.color = PdfColors.blue,
+    this.lineWidth = 2,
+    this.drawLine = true,
+    this.drawPoints = true,
+    this.isCurved = false,
+    this.smoothness = 0.35,
+  }) : assert(drawLine || drawPoints);
+
+  final List<LineChartValue> data;
+  final PdfColor pointColor;
+  final double pointSize;
+  final PdfColor color;
+  final double lineWidth;
+  final bool drawLine;
+  final bool drawPoints;
+  final bool isCurved;
+  final double smoothness;
+
+  void _drawLine(Context context, ChartGrid grid) {
+    if (data.length < 2) {
+      return;
+    }
+
+    PdfPoint t = const PdfPoint(0, 0);
+
+    final PdfPoint p = grid.tochart(data.first.point);
+    context.canvas.moveTo(p.x, p.y);
+
+    for (int i = 1; i < data.length; i++) {
+      final PdfPoint p = grid.tochart(data[i].point);
+
+      if (!isCurved) {
+        context.canvas.lineTo(p.x, p.y);
+        continue;
+      }
+
+      final PdfPoint pp = grid.tochart(data[i - 1].point);
+      final PdfPoint pn =
+          grid.tochart(data[i + 1 < data.length ? i + 1 : i].point);
+
+      final PdfPoint c1 = PdfPoint(pp.x + t.x, pp.y + t.y);
+
+      t = PdfPoint(
+          (pn.x - pp.x) / 2 * smoothness, (pn.y - pp.y) / 2 * smoothness);
+
+      final PdfPoint c2 = PdfPoint(p.x - t.x, p.y - t.y);
+
+      context.canvas.curveTo(c1.x, c1.y, c2.x, c2.y, p.x, p.y);
+    }
+  }
+
+  void _drawPoints(Context context, ChartGrid grid) {
+    for (final LineChartValue value in data) {
+      final PdfPoint p = grid.tochart(value.point);
+      context.canvas.drawEllipse(p.x, p.y, pointSize, pointSize);
+    }
+  }
+
+  @override
+  void paintBackground(Context context, ChartGrid grid) {}
+
+  @override
+  void paintForeground(Context context, ChartGrid grid) {
+    if (data.isEmpty) {
+      return;
+    }
+
+    if (drawLine) {
+      _drawLine(context, grid);
+
+      context.canvas
+        ..setStrokeColor(color)
+        ..setLineWidth(lineWidth)
+        ..setLineCap(PdfLineCap.joinRound)
+        ..setLineJoin(PdfLineCap.joinRound)
+        ..strokePath();
+    }
+
+    if (drawPoints) {
+      _drawPoints(context, grid);
+
+      context.canvas
+        ..setColor(pointColor ?? color)
+        ..fillPath();
+    }
+  }
+}

@@ -18,86 +18,6 @@
 
 part of widget;
 
-bool _isSortedAscending(List<double> list) {
-  double prev = list.first;
-  for (double elem in list) {
-    if (prev > elem) {
-      return false;
-    }
-    prev = elem;
-  }
-  return true;
-}
-
-class Chart extends Widget {
-  Chart({
-    @required this.grid,
-    @required this.data,
-  });
-
-  final ChartGrid grid;
-
-  final List<DataSet> data;
-
-  PdfPoint _computeSize(BoxConstraints constraints) {
-    if (constraints.isTight) {
-      return constraints.smallest;
-    }
-
-    double width = constraints.maxWidth;
-    double height = constraints.maxHeight;
-
-    const double aspectRatio = 1;
-
-    if (!width.isFinite) {
-      width = height * aspectRatio;
-    }
-
-    if (!height.isFinite) {
-      height = width * aspectRatio;
-    }
-
-    return constraints.constrain(PdfPoint(width, height));
-  }
-
-  @override
-  void layout(Context context, BoxConstraints constraints,
-      {bool parentUsesSize = false}) {
-    box = PdfRect.fromPoints(PdfPoint.zero, _computeSize(constraints));
-
-    grid.layout(context, box.size);
-  }
-
-  @override
-  void paint(Context context) {
-    super.paint(context);
-
-    final Matrix4 mat = Matrix4.identity();
-    mat.translate(box.x, box.y);
-    context.canvas
-      ..saveContext()
-      ..setTransform(mat);
-
-    grid.paintBackground(context, box.size);
-    for (DataSet dataSet in data) {
-      dataSet.paintBackground(context, grid);
-    }
-    for (DataSet dataSet in data) {
-      dataSet.paintForeground(context, grid);
-    }
-    grid.paintForeground(context, box.size);
-    context.canvas.restoreContext();
-  }
-}
-
-abstract class ChartGrid {
-  void layout(Context context, PdfPoint size);
-  void paintBackground(Context context, PdfPoint size);
-  void paintForeground(Context context, PdfPoint size);
-
-  PdfPoint tochart(PdfPoint p);
-}
-
 class LinearGrid extends ChartGrid {
   LinearGrid({
     @required this.xAxis,
@@ -107,7 +27,7 @@ class LinearGrid extends ChartGrid {
     this.textStyle,
     this.lineWidth = 1,
     this.color = PdfColors.black,
-    this.separatorLineWidth = 1,
+    this.separatorLineWidth = .5,
     this.separatorColor = PdfColors.grey,
   })  : assert(_isSortedAscending(xAxis)),
         assert(_isSortedAscending(yAxis));
@@ -132,6 +52,17 @@ class LinearGrid extends ChartGrid {
   double yOffset;
   double yTotal;
 
+  static bool _isSortedAscending(List<double> list) {
+    double prev = list.first;
+    for (double elem in list) {
+      if (prev > elem) {
+        return false;
+      }
+      prev = elem;
+    }
+    return true;
+  }
+
   @override
   PdfPoint tochart(PdfPoint p) {
     return PdfPoint(
@@ -216,78 +147,3 @@ class LinearGrid extends ChartGrid {
   @override
   void paintForeground(Context context, PdfPoint size) {}
 }
-
-@immutable
-abstract class ChartValue {
-  const ChartValue();
-}
-
-class LineChartValue extends ChartValue {
-  const LineChartValue(this.x, this.y);
-  final double x;
-  final double y;
-
-  PdfPoint get point => PdfPoint(x, y);
-}
-
-abstract class DataSet {
-  void paintBackground(Context context, ChartGrid grid);
-  void paintForeground(Context context, ChartGrid grid);
-}
-
-class LineDataSet extends DataSet {
-  LineDataSet({
-    @required this.data,
-    this.pointColor = PdfColors.blue,
-    this.pointSize = 3,
-    this.lineColor = PdfColors.blue,
-    this.lineWidth = 2,
-    this.drawLine = true,
-    this.drawPoints = true,
-  }) : assert(drawLine || drawPoints);
-
-  final List<LineChartValue> data;
-  final PdfColor pointColor;
-  final double pointSize;
-  final PdfColor lineColor;
-  final double lineWidth;
-  final bool drawLine;
-  final bool drawPoints;
-
-  double maxValue;
-
-  @override
-  void paintBackground(Context context, ChartGrid grid) {
-    if (drawLine) {
-      LineChartValue lastValue;
-      for (LineChartValue value in data) {
-        if (lastValue != null) {
-          final PdfPoint p1 = grid.tochart(lastValue.point);
-          final PdfPoint p2 = grid.tochart(value.point);
-          context.canvas.drawLine(p1.x, p1.y, p2.x, p2.y);
-        }
-        lastValue = value;
-      }
-
-      context.canvas
-        ..setStrokeColor(lineColor)
-        ..setLineWidth(lineWidth)
-        ..setLineCap(PdfLineCap.joinRound)
-        ..setLineJoin(PdfLineCap.joinRound)
-        ..strokePath();
-    }
-
-    if (drawPoints) {
-      for (LineChartValue value in data) {
-        final PdfPoint p = grid.tochart(value.point);
-        context.canvas
-          ..setColor(pointColor)
-          ..drawEllipse(p.x, p.y, pointSize, pointSize)
-          ..fillPath();
-      }
-    }
-  }
-
-  @override
-  void paintForeground(Context context, ChartGrid grid) {}
-}

@@ -33,6 +33,7 @@ void main() {
   group('LineChart test', () {
     test('Default LineChart', () {
       pdf.addPage(Page(
+        pageFormat: PdfPageFormat.standard.landscape,
         build: (Context context) => Chart(
           grid: LinearGrid(
             xAxis: <double>[0, 1, 2, 3, 4, 5, 6],
@@ -53,6 +54,7 @@ void main() {
 
     test('Default LineChart without lines connecting points', () {
       pdf.addPage(Page(
+        pageFormat: PdfPageFormat.standard.landscape,
         build: (Context context) => Chart(
           grid: LinearGrid(
             xAxis: <double>[0, 1, 2, 3, 4, 5, 6],
@@ -95,6 +97,7 @@ void main() {
 
     test('ScatterChart with custom points and lines', () {
       pdf.addPage(Page(
+        pageFormat: PdfPageFormat.standard.landscape,
         build: (Context context) => Chart(
           grid: LinearGrid(
             xAxis: <double>[0, 1, 2, 3, 4, 5, 6],
@@ -110,7 +113,7 @@ void main() {
               drawLine: false,
               pointColor: PdfColors.red,
               pointSize: 4,
-              lineColor: PdfColors.purple,
+              color: PdfColors.purple,
               lineWidth: 4,
             ),
           ],
@@ -120,6 +123,7 @@ void main() {
 
     test('ScatterChart with custom size', () {
       pdf.addPage(Page(
+        pageFormat: PdfPageFormat.standard.landscape,
         build: (Context context) => SizedBox(
           width: 200,
           height: 100,
@@ -141,6 +145,29 @@ void main() {
         ),
       ));
     });
+
+    test('LineChart with curved lines', () {
+      pdf.addPage(Page(
+        pageFormat: PdfPageFormat.standard.landscape,
+        build: (Context context) => Chart(
+          grid: LinearGrid(
+            xAxis: <double>[0, 1, 2, 3, 4, 5, 6],
+            yAxis: <double>[0, 3, 6, 9],
+          ),
+          data: <DataSet>[
+            LineDataSet(
+              drawPoints: false,
+              isCurved: true,
+              data: const <LineChartValue>[
+                LineChartValue(1, 1),
+                LineChartValue(3, 7),
+                LineChartValue(5, 3),
+              ],
+            ),
+          ],
+        ),
+      ));
+    });
   });
 
   tearDownAll(() {